I'm the first voter for Sonic vs. Samus. Before that we weren't even sure that 50/50 matches were possible.
Edit: As far as Starcraft vs. Halo... I thought its victory over Wind Waker was more notable, as hardly anybody saw that one coming. And Sub-Zero over Master Chief was actually a bigger R1 upset than Starcraft over Halo.
"Ah, a party! We haven't had one of those. It could be fun! So... what is a party?"
"You drink punch and eat CAKE! ...I think."